The Lebanon express. (Lebanon, Linn County, Or.) 1887-1898, 1887-07-15
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ras@ rnna@ncs or >Atmo<ph~rfc Pressure
Upon AIT Kinds or building stones.
The dissolving power of atmospheric
moisture seems to depend greatly upon
the quantity Of free tarbonic acid gas
1t holds in solution; and though this
quantity In any given volume of water
be extremely minute. in course of time
every substance which h1s an affinity
for it will yield more or less to it's ac-
ton. The s;licates of potash and soda,
for instance, which ars present IN the
igneous rocks--or, To dwell especiall,
on the class of materials under our mo-
tice in the Devonsh're granites-are
easily decomposed Wien rain water
falls upon them, and. the field spar
being removed mechanically by any OF
the countless actions of nature. it leav es
the other ingredients of the material
exposed TO the mechanical disintegra-
tion of changes of temperature. The
simple carbonates Of lime. again, some
times absorb carbonio acid with much
avidity, and pass into the state OF the sol
uble bicarbonates; and thus. in proper
ton as the original face of the stone is
removed, does the lower surface be-
come exposed to the action of the rain.
The rain water of such town rs Lon
don not only does contain large guam
titles of free carbonic acid. but II also
contains sulphuric acid and ammonia,
which are capable of exercising a very
deleterious influence upon the carbon
ates of lime. In discussing. however,
the effects of these agents upon build
ing stoves. it is essential tn bear in
mind the fact that the mechanical stat
of the elements of those material
greatly modifies their resistance.
Those which are of crystalline char
acter do not yield so readily as thos
which are amorphous, and the crystal
lization produced by volcanic or plu
tonic influence appears to BE- even
more permanent than that which take.
place in the ordinary way. L
follows from these considera-
tions that the stones of an irre :
ular. confused. earthly texture, which
are able 70 absorb consider tble q anti
ties of moisture, and which contain
silica in soluble form. or ihs car
Donate of lime. shoald never be en-
ployed in positions where rain water
could lodge upon them. beat against
them, or be taken up from exgerna'
sources by capillary Or oh II ac,ipn.
In positions exposed To any of the ab W..
dangers, none but non-absorb .nt and
decidedly crystalline materials shaul
lie used. End rs those qualities are ~
most exclusively poss ssse by d .nsc
stones, it may be considered that the
mere specific gravity af n stone is !,
pr1nia taeie indication of its construct
i've value. But atmospheric mois,ur..
when absorbed into buililing ones.
acts upon them quite rs much through
the changes in its own volume. in pass
ing from the liquid to the solid st lte at
the time of frost, as it does by the
chemical dissolution it produces
If the stone should be
placed in such manner as that
water should accumulate in anv D r
eeptible quantities between its various
layers, a ID if the position of those lav-
ers be such that the expansion of the
water in freezing can not take place
freely, the respective layers containing
the water will be violently le,ac,.e
from one another
Now all ston,s. even the crystalline
limestones and states, have certain
planes or directions of cleavage or of
strat.fcation. along which water Il ,wS
more readily than in any other course
If the stones be placed in bal ling
with those planes in direction likely
TO retain rain fa ling upon. or absorb d
through the surface (Which is th ease
when stones are placed "bed to wealth
er }. disintegration must ensue unless
the edges of the he Ia be left free. and
even in that case there is danger of
frost detaching one layer fro II anoth-
er.-G. r. BuTneH. IA 5rchf eck